bonding/grounding PV framing on roof

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SceneryDriver

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Electrical and Automation Designer
A colleague asked me the other day if it was code compliant to bond the PV array frames (aluminum) on a roof to a separate ground rod, and connect them with #4 stranded copper. I told him that the frames need to be bonded to the GEC by landing on the AC panel's ground bar. Was I correct; solar is not in my wheelhouse?


SceneryDriver
 
SceneryDriver said:
A colleague asked me the other day if it was code compliant to bond the PV array frames (aluminum) on a roof to a separate ground rod, and connect them with #4 stranded copper. I told him that the frames need to be bonded to the GEC by landing on the AC panel's ground bar. Was I correct; solar is not in my wheelhouse?


SceneryDriver
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They actually need to be bonded via the EGC system (as opposed to the GEC), and then to the inverter's(s') dc ground connection point. The GEC, where required, connects among the inverters, and then to the premises wiring electrode. Inverters with integrated isolation transformers require this, and by contrast non-isolated inverters only require the AC EGC.

In 2014, it was required by a controversial rule to connect to an additional grounding electrode. In 2017, it is optional. In any case, it is counterproductive to safety to bond to a ground rod that is not also bonded to the premises wiring electrode(s), through a path other than the EGC.
 
Carultch said:
They actually need to be bonded via the EGC system (as opposed to the GEC), and then to the inverter's(s') dc ground connection point. The GEC, where required, connects among the inverters, and then to the premises wiring electrode. Inverters with integrated isolation transformers require this, and by contrast non-isolated inverters only require the AC EGC.

In 2014, it was required by a controversial rule to connect to an additional grounding electrode. In 2017, it is optional. In any case, it is counterproductive to safety to bond to a ground rod that is not also bonded to the premises wiring electrode(s), through a path other than the EGC.
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I meant to type EGC and I fat-fingered it. :blink:

I will have him check to see if there's also a connection to the EGC - their may be, but up on the roof where he couldn't see. Thanks. I will let him know.



SceneryDriver
 
Yes, you have to bond the array by EGC to the inverter and eventually the AC grounding system.

But just to confuse you, in the 2014 NEC you are also suppose to ground the array to a separate electrode as your friend described (except you don't need to use a #4 GEC, I don't know where everyone gets that from). This is a stupid requirement in my opinion and if you google '690.47 Danger' you'll find out via YouTube why the host of this forum agrees and why it was removed from the 2017 NEC. For a rooftop array try to get your inspector to agree to Exception 1 since the structure already has a GES and say your new electrode isn't 6ft from the building.
 
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